Add an audio file to and mkv video

Then use mkvmerge from the installation to mux audio and video into the mkv container from the command line.

There is also a Gui tool, mkvtoolnix-gui that is a front end to mkvtoolnix.

sudo apt-get-install mkvtoolnix-gui

Example to mux video file called, input-video.mkv with a sound file called soundfile.mp3, creating a new muxed mkv file called output-with-sound.mkv, do the following in the directory where you have the video without audio and the audio file:

mkvmerge -o output-with-sound.mkv -A input-video.mkv soundfile.mp3

More examples including synchronization here: http://www.bunkus.org/videotools/mkvtoolnix/doc/mkvmerge.html

Then use mkvmerge from the installation to mux audio and video into the mkv container from the command line.

There is also a Gui tool, mkvtoolnix-gui that is a front end to mkvtoolnix.

sudo apt-get-install mkvtoolnix-gui

Example to mux video file called, input-video.mkv with a sound file called soundfile.mp3, creating a new muxed mkv file called output-with-sound.mkv, do the following in the directory where you have the video without audio and the audio file: